Writers who have changed my life, and the books I loved most reading (I apologize in advance for blatantly breaking the rules here, but every book I read and love changes me.)

Louise Penny - The entire Armand Gamache series.
Kurt Vonnegut- All of his books, but especially loved Cat's Cradle.
J.D. Salinger - Franny and Zooey, Raise High the Roofbeam Carpenters
Ursula K. Le Guin - The king of all books I've ever read is her Lathe of Heaven. Also loved The Left Hand of Darkness.
Robert Heinlein - The Moon is a Harsh Mistress (a heartbreaker, and can still make me cry), Red Planet, Podkayne of Mars
Isaac Asimov - I Robot, and its sequels
Arthur C. Clarke - Childhood's End
Margaret Atwood - The Handmaids Tale
Dana Stabenow - the entire Kate Shugak series
Ray Bradbury - Fahrenheit 451, Something Wicked This Way Comes

Then there's To Kill a Mockingbird, Cry the Beloved Country, A Wrinkle In Time, The Picture of Dorian Gray...

Life is made of books.

The bible, because of it I've become closed minded and stupid. Trying to undo the damage.

"Childhood's End" by Arthur C. Clarke. It impacted my life in that I had a better sense of my real place in the universe, although it was fictional. Not incompatible with becoming atheist and realizing that I was just another grain of sand and not one of "God's children." I was torn between what should be the apparent evil of our children being stolen away from the earth and a bigger picture of the universe moving forward.

Also so hard to choose one. However I guess if I have to choose one I would have to say The Three Musketeers
by Alexandre Dumas. Not because it gave me any major life eurekas, but it was the book that hooked me on reading.

Dick and Jane. They taught me how to read.

Atlas Shrugged. I came to realize that my needs are just as important to me, as others' needs are important to them. I stopped "sitting in the back of the bus".

Portnoy’s Complaint, because it introduced me to Philip Roth.

The Naked Ape. It completely blew the last vestiges of religion which haunted me out the door never to return. (I wasn't exposed to Darwin in public school.)

The Lord of the Rings Trilogy back in the early 70's. I think it spoiled me for every other book of fiction. I feel as though I started at the top and had no place else to go but down.

The Prince by Machiavelli showed me how to think more seriously about relationships.
The Golden Notebook by Doris Lessing because she so clearly showed a woman's psychology.
The Falls by Joyce Carol Oates because it's Oates at her best showing the agony of being human.
Oh, you said one. I'll stop now.

My check book, because it doesn't have enough money in it.

I have to say that there was a book for different stages of my life. In Third grade, Nancy Drew introduced me to solving mysteries and I have been hooked ever since. Of course, I was already familiar with Superman, and Action Comics, but the summer after fourth grade, I discovered Isaac Asimov and Robert Heinlein and it was all over.
After I began working, and failed at the first job I had really wanted to succeed at, I found a book called "I'm running away from home, but I'm not allowed to cross the street". It was the early 1970's, and that book showed me how unprepared I was to try to break into the 'Old Boys Club' which was alive and well in the insurance capital of the world in 1972. Shortly after that, I read a book called "My Mother, Myself". Also eye-opening. made me realize how sometimes our mother is not necessarily our mother, but the person who mothers us - a complicated but fascinating concept which has helped me understand many things about myself and others as well.
I've found that at other stages of my life, I seem to find or be given books that help me through those times with some valuable insight or other. Many happy returns have come from good books!

Easy peasy. Atlas Shrugged. I was in the Marines. Still love it.

Probably Slaughterhouse Five by Kurt Vonnegut as far as idealogy goes.

A Long Way Gone by Ishmael Beah. It's a hard read. And, gave me,pause in my journey to re-align my big priorities.

The Discworld series by Terry Pratchett. One book in particular - Night Watch.

I don't have any personal role models or heroes, but if I had to choose one, it would be Commander Vimes of the City Watch. As he describes himself: "tarnished but not rotten"...

A book of Edgar Allan Poe Stories my mom read to us from when she was teaching us to read.

The Fountainhead

That would be the Selfish Gene by Richard Dawkins, it helped me acquire a real scientific view of the world, which turned out to be even grander that the religious view, i think that's when I became truly spiritual.

The Culture of Make Believe, Derrick Jensen

Author is an extremely erudite environmentalist who knows how to stir the mind to action.

An early chapter is the real true story about blood diamonds. You will never think about diamonds in the same way again and you will want to sell yours or throw it away.

My science book because it open up the universe for me to study

Saharasia by James DeMeo, Phd.

It is his well founded theory on origins of warfare, child abuse, subjugation of women etc. in the old world deserts.

In 1974, my Dad gave me a copy of The Book: On the Taboo Against Knowing Who You Are, by Alan Watts. It started me on a lifetime of thinking about the big questions.

Why am I not Christian, by Bertrand Russell...... It was an eye opener in my teens. No turning back from there....

oooooh hard one. Umm there are definite a few that come to mind, not sure if I can break it down to just one. Here's the top ones though.

-- Whipping Girl: A Transexual Woman on Sexism and the Scapegoating of Femininity by Julia Serano
-- Against His-Story Against Leviathan by Fredy Perlman
-- Anarchist Morality by Peter Kropotkin
-- The Technological Society by Jacques Ellul